Apparatus for handling magnetically attractive material

ABSTRACT

Apparatus for handling material by magnetic attraction comprising an elongated tubular member of nonmagnetic material with a magnet slidably received in the tubular member. The magnet is movable along the length of the tubular member between starting and dwell positions to carry magnetically attractive articles or material along the tubular member. A nonmagnetic barrier engages the tubular member between the starting and dwell positions to prevent the articles or material attracted by the magnets from moving past the position of the barrier as the magnet moves past the barrier to the dwell position.

mted States Patent 1 1 1 1 ,712,472 Elliott 51 Jan. 23, 1973 [541 APPARATUS FOR HANDLING Y 3,537,586 11 1970 Hunkeler ..210/222 MAGNETICALLY ATTRACTIVE 3,616,922 11/1971 Tumock ..210/222 MATERIAL I P E R b F d rt'ma'ry xammeren en me man [76] I lnvemon E! -r 4 Maryland Assistant Exahiiner-T. A. Granger woma At'tomey--McGlynp, Reising, Milton & Ethington [22] Filed: Dec. 16, 1970 211 App]. 196598498 [57] ABSTRACT Apparatus for handling material by magnetic attrac- 52 us. (:1 ..210/222, 198/41, 271/63 A el(WE-med tubular member 511 1m. (:1. ..B01d 35/06 magnetic with a magnet slidably received in [58] m i of Search 210/222, 22 209/217, 2 the tubular member. The magnet is movable along the 209 22 193 41; 271 3 A length of the tubular member between starting and dwell positions to carry magnetically attractive articles [56] R f n Cit d or material along the tubular member. A nonmagnetic barrier engages the tubular member between the start- UNlTED STATES PATENTS ing and dwell positions to prevent the articles or 2,736,432 2/l956 Gardes ..210 222 material attracted by the magnets from moving P 3,121,683 2/l964 Fowler..... the position of the barrier as the magnet moves past 3,143,496 8/1964 Maretzo the barrier to the dwell position. 3,282,424 ll/l966 Mitchell 3,428,179 2/1969 Boyd, Jr.-et al. ..210/222 31 Claims, 14 Drawing Figures PATENTEDJAN23 I973 3,712,472

sum 3 OF 5 I N VENTOR.

71022 6. E/brt Y Mia? 0&7

ATTORNEYS PATENTEDJAH 23 I915 SHEET UF 5 TO RNEYS PATENTHJJAN23 W5 3,712,472

SHEET 5 [IF 5 l N VEN TOR.

ATTORN APPARATUS FOR HANDLING MAGNETICALLY ATTRACTIVE MATERIAL x Existing apparatus forperfortning this function is expensive to operate, and requires high maintenance cost. a i a There are also many operations in industry requiring the frequent movement of material from one fixed location to another for further processing, storage, packaging or shipment. For example, in the handling of sheet material, it is frequently necessary to move the sheet material from one location to another location where it is stacked for storage or shipment. In some factories and manufacturing plants, it is necessary to move parts, scrap and other material over the same route between two locations.

An object of this invention is to provide apparatus for handling material by magnetic attraction wherein magnets are slidably received in nonmagnetic tubes so that movement of the magnets through the tubes can cause magnetically attractive material or carts or carriages tomove along the length of the tubes.

Another object is to provide the apparatus for handling material by magnetic attraction wherein all of the moving parts canv be-completely enclosed and protected from liquid, dust, and other deleterious substances.

' Another object is to provide apparatus forhandling material by magnetic" attraction wherein a magnetic member is caused to move along a fixed path, the mag,-

propelling force for moving the material to be handled, themagnet being enclo'sedby nonmagnetic material so that movement of the magnetic me'mber'beyond a barrier engaged by material attracted to the magnet will release the material from the field of the magnetic member.

in carrying out the foregoing, and other objects of the invention, apparatus according to the present invention includes an elongated tubular member of nonmagnetic material with a magnet slidably received in the tubular member for movement along the. length thereof between a starting position near one endof the tubular member, and a dwell position near the other end thereof. The magnetis operable to attract-articles of magnetically responsive material externally of the tubular member when the magnet is caused tomove netic field of the magnetic member serving as the between the starting and dwell positions. A-barrier engagesthe tubular member between the starting and dwell positions for preventing articles and material moved along the tubular ,member'by the magnet from moving past the position of the barrier as the magne moves past the barrier to the dwell position.

in one arrangement, themagnet is in the form of a piston, having a'generally'fluid-tight relationship. with: the innersurface of the tubular. member, and is caused to: move throughthe tubular member bya fluid flow,

system. The fluid flow system is connected with the tubular member and is selectively operable to cause fluid flow in opposite directions through the tubular member, the fluid flow forcing the magnetic piston to move in the direction of flow through the tubular member. The fluid system includes a reservoir, a pump for delivering fluid from the reservoir and a valve for controlling the direction of flow of fluid from the pump through the tubular member.

in one embodiment of the invention, the magnet is caused to move through the tube by mechanical apparatus, including a pair of shafts extending transversely to the tube with a flexible connector having one and connected withone of the shafts and its other end connected with a magnet, and a second flexible connector having one of its ends connectedwith the other shaft and its other end connected with the magnet. Simultaneous rotation of the shafts in one direction causes one of the flexible connectors to wind around its shaft and the other flexible connector to simultaneously unwindfrom its shaft, and the magnet is carried through the tubes-by thewinding and unwinding of the respective connectors. One of the shafts is powered by a motor to rotate in one direction, and the other shaft is spring loaded to resist rotation in the direction of the powered rotation of the shafts. Consequently, when the motor causes the shaft to rotate in one direction to move the magnet from the starting position to the dwell position, and is then turned off, the spring causes the magnet to return from the dwell position to the starting position. A

One specific embodiment of the invention includes a container for a mixture of magnetically attractive material and nonmagnetic material; a pair of spaced parallel manifolds of nonmagnetic material with a plu.- rality of spaced, parallel tubes of nonmagnetic material extending between the manifolds, each end of each tube being in fluid communication with one of the manifolds. A magnetic piston is received in each of the tubes anda fluid flow system is connected with the manifold including a valve which is selectively operable to cause fluid flow in opposite directions through the tubes to cause movement of the magnetic pistons in the same direction. One of the manifolds is supported in thecontainer and the other manifold is located outside the container. A nonmagnetic barrier is mounted on the tubes outside the container for engaging magnetically attractive material carriedfrom the container by the magnetic attraction of the pistons as the pistons move from the manifold within the container toward the manifold that is located outside the container. As the pistons move past the barrier, the material carried from the container is released from themagne'tic field.

When the tubes are located in substantially vertical position with respect to the container of magnetic and nonmagnetic material, oneembodiment of the invention includes a shaft mounted on the tubes and extendi'ng transversely with respect to the tubes, and a plurality of rollers of magnetic material mounted on the shaft and spaced from each other such that each of the rollers is received between an adjacent pair of tubes of the shaft, the rollers being located. outside the container near the barrierso as to collect by magnetic attraction material falling from the barrier. A chute having a slot for receivingeach. of the rollers with the edge of the slots being disposed in close, wiping contact with the rollers, wipes the material collected onto the magnetic rollers from the surfaces of the rollers as the rollers rotate through the slots, and the material wiped from the rollers is conducted by the chute to a container or remote location.

In another embodiment of the invention, the apparatus includes a plurality of spaced parallel tubes of nonmagnetic material with a magnet slidably received in each of the tubes. A plurality of rollers, each of which is mounted between an adjacent pair of the tubes, is rotatable about an axis transverse to the tubes. The rollers are spaced from each other along the length of the tubes with the periphery of each roller projecting beyond the outer periphery of the tubes for supporting sheet material attracted by the magnets. As the magnets move through the tubes, the sheet material moves along the rollers until striking a nonmagnetic barrier. As the magnets move past the barrier, the sheet material is released from the magnetic field and drops from the tubes, the sheets being successively stacked beneath the tubes.

In another embodiment of the invention particularly suitable for handling sheet material, a plurality of tubes of nonmagnetic material is disposed in substantially horizontal relationship above a floor with a magnet slidably received in each of the tubes. A magnetically attractive sleeve member is concentrically mounted on each of the tubes with antifriction means in the form of balls carried by the sleeve, the balls supporting the sleeves for substantially frictionless movement along the tube in response to movement of the respective magnets in the tubes. Sheet material attracted by the magnetic field of the magnets engages the sleeve members and is carried by movement of the sleeve members along the lengths of the tube due to the magnetic attraction between the magnets and the sleeve members until the magnets move past the barrier to release the sheet from the magnetic field and permit them to drop from the tubes and sleeve members. When the magnets are returned to the other end of the tubes, the sleeves are carried to the starting position due to the magnetic attraction.

Another specific arrangement for moving material from one location to another includes tubes of nonmagnetic material with a magnet slidably received in each of the tubes and a material transporting carriage movably mounted on the tubes. The carriage has magnetic attractive elements for causing movement of the carriage in response to movement of the magnets in the tubes. As the magnets are forced to move through the tubes, the carriage is carried by the magnetic attraction along the length of the tube.

Other objects, advantages and features of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 illustrates an arrangement for separating magnetically attractive particles from nonmagnetic material by apparatus embodying the invention;

FIG. 2 is a perspective view of the separating apparatus used in FIG. 1;

FIG. 3 illustrates another arrangement for separating magnetically attractive particles from nonmagnetic material;

FIG. 4 is a view taken along lines 4-4 of FIG. 3;

FIG. 5 is an elevational view of apparatus according to the invention as utilized in handling sheet material;

FIG. 6 is a view taken along lines 6-6 of FIG. 5;

FIG. 7 is an enlarged detailed view of a modified version of the arrangement of FIGS. 5 and 6;

FIG. 8 is a sectional view taken along lines 8--8 of FIG. 7;

FIG. 9 is an elevational view, partially in section, of another embodiment of the invention;

FIG. 10 is a view taken along lines 10-10 of FIG. 9;

FIG. 11 is a sectional perspective view of an alternative arrangement;

FIG. 12 is a view, partially in section, of an altemative construction embodying the invention; and

FIG. 13 is a sectional view taken on lines 13-13 of FIG. 12.

In FIG. 1, the invention is utilized to separate ferrous or magnetically attractive particles from a liquid. Reference numeral 2 designates a container for a mixture of magnetically attractive material and non-magnetic material, the nonmagnetic material being a liquid in the illustrated system. Container 2 has a bottom wall 4, an inclined end wall 6, a vertical end wall 8, and a cover 10. A wire 12 projects upwardly from the bottom wall 4 of the container 2. The liquid containing the metallic particles is fed into the container 2 by a conduit l4, and the cleaned liquid is removed through a conduit 16 from the opposite side of the weir 12 from the conduit 14.

The magnetically attractive particles are removed from the liquid by apparatus designated generally by reference numeral 18 supported at its lower end of the container 2. The apparatus 18 includes a plurality of spaced, parallel tubes 20 of nonmagnetic material; a magnet 22 supported in each of the tubes 20 for reciprocable movement along the length thereof; and means designated generally by reference numeral 24 for moving the magnets 22 simultaneously in a selected direction through the respective tubes 20. Apparatus 18 includes a transverse manifold at each end of the group tubes 20 which secures the tubes together in spaced parallel relationship. The manifold at the lower end is designated by reference numeral 26, and the manifold at the upper end is designated by reference numeral 28. Manifold 26 is shown in FIG. 1 as being supported on the support bracket 19.

The magnets 22 define pistons in the tubes 20, and the means 24 for moving the magnets comprises a fluid flow system connected with the manifolds 26 and 28 which is selectively operable to cause fluid flow in opposite directions in the tubes 20 to cause corresponding movement of the respective magnets 22.

Again referring to FIG. 1, when the magnets 22 are located in the portions of the respective tubes 20 received in the container 2, the particles of magnetically attractive material are attracted to the outer surface of the tubes 20 by the field of the magnets 22. As the magnets 22 are caused to move toward the manifold 28 from the manifold 26, the particles are carried upwardly from the liquid toward the upper end of the tubes 20. Apparatus 18 includes a barrier 30 located between the manifold 26 and 28 for stopping or interrupting movement of the particles or material attracted by the magnets as the magnets move between receiving one of the tubes to block passage of any material attracted by the magnets 22 as the magnets move past the barrier. As the magnets 22 move past the barrier 30 as shown in FIG. 1, any particles carried to the barrier by the magnets 22 are released from the magnetic field so that they can fall into a collection bin or container 32. An air or water spray device 34 may be employed to assist in removing any particles from the surface of the barrier 30.

The magnets 22 thus move cyclically from a starting position adjacent the manifold 26 to a dwell position adjacent the manifold 28 by fluid flow from the fluid flow system 24. When the magnets 22 are in the starting position adjacent manifold 26, fluid is caused to flow into the manifold 26 and force the magnets 22 to move upwardly along the lengths of the tubes 20 to the dwell position adjacent the upper manifold 28. The magnets remain in the dwell position adjacent manifold 28 until the flow is reversed in the system causing fluid to be introduced into manifold 28 forcing the magnets 22 to return to the starting position. Each time the magnets move from the starting position to the dwell position, magnetically attractive material is carried by the magnets to the barrier 30, which material falls into the collection bin 32 as the magnet 22 moves past the barrier to release the material from the field of the magnet. The magnets remain in the dwell position for a time adequate to permit removal of particles from the barrier 30.

The fluid flow system 24 is schematically illustrated inFIG. 2 and includes a reservoir 36 for hydraulic fluid, a pump 38 having its intake connected with the reservoir for delivering fluid from the reservoir, and a control valve 40 for controlling the direction of flow of fluid from the pump to the tubular members 20. The control valve 40 is illustrated in its neutral position in FIG. 2 wherein the output line 41 of the pump is connected with a return line43 so that fluid will return directly to the reservoir by the pump 38. The lines 42 and 44 connected respectively with manifold 26 and 28 are blocked sothat fluid cannot flow in either direction in these lines. j

When valve 40 is shifted to the right from the neutral position shown in FIG. 2, the output line 41 is connected with line 42, and line 44 is connected with the return line 43 so that fluid is pumped by pump 38 into manifold 26 and is'drained from manifold 28 as the magnets 22 move upwardly in the respective tubes 20. Conversely, when the valve 40 is shifted to the left from the position shown-in FIG. 2, the output line 41 is connected with line 44 and the drain line 43 is connected with line 42 so that fluid is pumpedinto manifold 28 through line 44 and is drained from manifold, 26 through the drain line 43. Relief valves 46 and 48 may also be provided in the lines 42 and 44, respectively, to return excess fluid to the reservoir when the pump continues to run with the magnets located at either end of the tubes 20. 5

It may be desirable in some installations for the polarity of adjacent pairs of the magnetic pistons 22 to be reversed with respect to each other. By reversing the polarity of the adjacent pairs of magnets 22, a mutual attraction will be maintained between the magnets to assist in maintaining the magnets in aligned relationship with each other in the respective tubes against the tendency of any of the magnets to fall behind the other magnets, particularly when a heavy load of particles is being carried by any one particular magnet compared to the others.

The tubes 20 and barrier 30 may be of nonmagnetic stainless steel or other material. The magnets 22 may be permanent or electromagnets. Appropriate conductors may be provided within the tubes 20 to connect the magnets with a source of current when electromagnets are used instead of permanent magnets. The conductors may, for example, extend along the inner surfaces of the tubes, the magnets having a sliding electrical contact with the conductors.

Thus, FIGS. 1 and 2 disclose apparatus 18 for handling material by magnetic attraction comprising an elongated tubular member 20 of nonmagnetic material; a magnet 22 slidably received in the tubular member 20 for movement along the length thereof between a starting position (at 26) and a dwell position (at 28); means 24 for selectively moving magnet 22 in the tubular member 20 in opposite directions between the starting and dwell positions; and a barrier 30 on the tubular member 20 between the starting and dwell positions for preventing articles and other material attracted by the magnet 22 from moving past the position of the barrier as the magnet 22 moves to the dwell position.

More specifically, FIGS. 1 and 2 disclose apparatus 18 for separating magnetically attractive particles from non-magnetic material comprising a container 2 for a mixture of magnetically attractive material and nonmagnetic material; a pair of spaced parallel manifolds 26 and 28 of nonmagnetic material; a plurality of spaced, parallel tubes 20 of nonmagnetic material extending between said manifolds 26 and 28, each end of each tube 20 being in fluid communication with one of the manifolds; a magnetic piston 22 in each of the tubes 20; a fluid flow system 24 connected with the manifolds 26 and 28; .the fluid flow system being selectively operable to cause fluid flow in opposite directions through the tubes 20 to cause movement of the magnetic pistons 22 simultaneouslyin the same direction in the tubes 20; means 19 supporting one of the manifolds 26 in the container 2 with the other manifold 28 located outside the container 2; and a nonmagnetic barrier 30 mounted on the tubes 20 outside the container, the barrier 30 being engageable by magnetically attractive material carried from the container by the magnetic attraction of the pistons 22 as the pistons move from manifold 26 toward manifold 28 to release such material from the magnetic field of the pistons as the pistons move past the barrier 30 toward the other manifold 28.

FIGS. 3 and 4 disclose another arrangement embodying the invention wherein ferrous metallic fines, particles, or'chips are removed from liquid received in a container or tank 102. Reference numeral 118 collectively designates apparatus which may be of identical construction to the apparatus 18 of the embodiment of FIGS. 1 and 2. The apparatus 118 includes a pair of spaced parallel manifolds 126 and 128 of nonmagnetic material with a plurality of spaced, parallel tubes 120 extending between the manifolds, each end of each tube 120- being in fluid communication with the manifolds 126 and 128. A magnetic piston 122 is received in. each of the tubes for reciprocable movement along the length thereof. One of the manifolds 126 is located in the container 102 and the other manifold 128 is located outside the container. A nonmagnetic barrier 130 is mounted on the tubes 120 outside of the container and is engageable by magnetically attractive material carried from the container by the magnetic attraction of the magnets 122 as the magnets 122 move from a starting position at manifold 126 toward the other manifold 128. As the magnets move past the barrier toward manifold 128, material carried by the magnets from the container 102 is released from the magnetic field of the magnet 122.

A shaft 131 is rotatably mounted on brackets 132 carried by each of the tubes 120, and a plurality of rollers 134 of magnetic material is mountedon shaft 131. The magnetic rollers 134 are spaced from each other along shaft 131 such that each of the tubes 120 is received between an adjacent pair of rollers as shown in FIG. 4. As the magnets 122 move past barrier 130 toward the manifold 128, the magnetically attractive particles carried to the barrier 130 by the magnets 122 fall from the barrier 130 and are attracted to the surface of the rollers 134. Reference numeral 136 collectively designates a chute for removing material from the rollers 134 and conducting the material away from the rollers.

The chute 136 is inclined downwardly and has a slot 142 receiving each of the rollers 134 as shown in FIG. 4. The slots 142 have each of their edges in close, wiping relationship with the respective rollers 134 to wipe material from the surface of the rollers upon rotation of the rollers in a clockwise direction as shown in FIG. 3. The chute 136 is of nonmagnetic stainless steel or other nonmagnetic material and is inclined downwardly so that the material removed from the surfaces of the rollers 134 is carried by gravity to a collection bin located at the end of the chute. The weight of the material removed from the rollers 134 accumulates until it is sufficient to overcome the magnetic attraction of the rollers 134 which causes the material to slide down the chute 136.

FIGS. and 6 illustrate apparatus 218 for handling sheet material by magnetic attraction. The apparatus 218 may be of identical construction to the apparatus 18 and 118 of the previously described embodiments and includes a plurality of spaced, parallel tubes 220 of nonmagnetic material with a magnet 222 slidably received in each of the tubes 220. The tubes 220 extend between the manifolds 226 and 228 of nonmagnetic material, each of the tubes 220 being in communication at their ends with the manifolds 226 and 228.

Aplurality of rollers 232 is provided in FIGS. 5 and 6 for supporting sheet material S for movement along the length of the tubes, the movement of the sheets S resulting from the magnetic attraction between magnets 222 and the sheet S. Each roller 232 is mounted between an adjacent pair of the tubes 220 and is rotatable about an axis transverse to the tubes 220. The rollers 232 are spaced from each other along the length of the tubes, and the periphery of each of the rollers projects beyond the outer periphery of the tubes so that the sheet material S is held in spaced relationship from the surface of the tubes 220.

As shown in FIGS. 5 and 6, the tubes 220 are disposed in generally horizontal, spaced relationship with respect to a floor F, and a barrier member 230 projects into the path of sheet S moving toward the right in FIG. 5 to stop movement of the sheets carried along the tube by the attraction of the magnets 222 so that sheets are released from the magnetic field of magnets 222 as the magnets move past the barrier 230. As shown in FIG. 5, as the sheets S strike the barrier 230, they may be successively stacked in a container or storage rack as the magnets 222 move beyond the barrier 230 toward the manifold 228.

Some or all of the, rollers 232 may be of magnetic material to resist transverse movement of the sheets S with respect to the tubes 220, the magnetic force of the rollers 232 of course being insufficient to support the sheets S so that the sheets S fall from the tubes 220 when they are released from the field of the magnets 222.

As in the previously described embodiments of FIGS. 1 through 4, the magnets 222 may comprise piston members in the tubes, the manifolds 226 and 228 being connected with a fluid flow system as indicated by reference numeral 24 in FIG. 2.

FIGS. 7 and 8 illustrate an alternative arrangement particularly suitable for handling sheet material wherein a magnetically attractive carrier 236 is supported externally on each of the tubular members 220 for movement along the length of the tubes in response to movement of the magnets 222. The carrier member 236 comprises a sleeve member 238 concentrically receiving the tube 220. The sleeve member 238 is supported on the tube 220 by antifriction means in the form of balls 240 mounted in apertures formed in the wall of the sleeve member. The sleeve member and balls may be of nonmagnetic material, and magnetically attractive members 242 and 244 are mounted on each end of the sleeve member 238 so that the sleeve member is caused to move along the length of the tube 220 by the magnetic attraction of the moving magnet 222 within the tube 220. Members 242 and 244 are in the form of rings which may be of magnetically attractive material, the rings 242 and 244 being covered by resilient members 246 and 248, respectively.

As the magnets 222 move toward the right in FIG. 7 from manifold 226 to manifold 228, sheets S are supported on the carriers 236 until the resilient member 248 strikes the barrier 230. As the magnet 222 moves beyond the barrier 230, sheet 8 is released from the magnetic field of the magnet 220 and falls from the tube 220 as in the FIG. 5 embodiment. When the magnet 222 returns from manifold 228 to manifold 226, the carrier 236 is returned to the starting position at manifold 226 due to the magnetic attraction between the carrier 236 and magnet 222.

FIGS. 9 and 10 illustrate an arrangement wherein an external carrier 236 in the form of a material transporting carriage is supported externally on apparatus 318 which may be of identical construction to the apparatus 18, 118, and 218 of the previously described embodiments. Apparatus 318 includes a plurality of spaced, parallel tubes 320 of nonmagnetic material with a magnet 322 slidably received in each of the tubes 320. The material transporting carrier 336 is movably mounted on the tubes 320 such that the tubes 320 serve as a track for the carriage 336. Magnetically attractive means 348 is mounted on the carriage 336 for causing movement of the carriage along the tubes 320 in response to movement of the magnets 322 in the tubes 320.

A .pair of spaced parallel shafts 340 and 342 are mounted beneath the bed portion 338 of the carriage, the shafts extending transversely to the tubes 320. Rollers 344 are mounted on the shafts 340 and 342 for supporting the carriage on the tubes 320. The rollers 344 are each formed with a concave surface for engaging the respective tubes 320 and providing lateral support for the carriage 336.

Bracket members 346 depend from the carriage 336 between each adjacent pair of tubes320 for supporting the magnetically attractive means which is in the form of external magnets 348. The external magnets 348- have their polarity reversed with respect to the magnets 322 as illustrated in FIG. 10. That is to say, the North pole of the magnets 322 is disposed adjacent the South pole of the magnets 348, and vice versa.

A retainer designated generally by reference numeral 350 projects beneath the carriage 336 and receives the outermost tube 320 to prevent displacement of the carriage with respect to the tube, while at the same time permitting pivotal movement of the carriage about the tube received by the retainer 350. The retainer 350 includes a pair of oppositely curved arms 352 and 354 which loosely receive the left-hand tube 320. Consequently, the carriage can be pivoted about the left-hand tube to a dump position to dump material supported in the carriage 336.

As the magnets 322 move away from the manifold 326, the carriage 336 is caused to move with the magnet 322 due to the mutual attraction between magnets 322 and 348. When the carriage stops, a hydraulic piston and cylinder member indicated by reference numeral 360 in FIG. 9 may be actuated to extend and pivot the carriage 336 about the left-handtube 320 to a dump position. As in the previously described embodiments, the carriage may be caused to strike a barrier to stop movement of the carriage 336 and release the car.- riage'336 from the magnetic field of the magnets 322 as the 'rnagnets322 move past the barrier. When the magnets 322 are caused to return to the manifold 326 and pass the barrier on their return trip, the carriagewill be returned to its starting position at manifold 326.

FIGS. 11 and 12 illustrate an embodiment of the invention in which the magnets are moved mechanically through the tubes instead of hydraulically. Reference numeral 418 collectively designates apparatus, for handling material by magnetic attraction comprising a plurality of spaced, parallel tubes 420 of nonmagnetic material; a magnet 422 supported in each of the-tubes 420 for reciprocable movement along the length extending through one end of the respective tubes 420 and connected with the magnet 422 therein; a second set of elongated flexible connectors 440, each of which has one end connected with shaft 438 and its other end extending through the opposite end of the respective tube 420 from the corresponding connector 436 and connected with the magnet 422 therein such that simultaneous rotation of shafts 434 and 438 in one direction causes the first set of flexible connectors 436 to wind around shaft 434 and the other set of flexible connectors 440 to unwind from shaft 438 to cause movement of the magnets 422 toward the right in FIG. 11. Simultaneous rotation of shafts 434 and 438 in the opposite direction causes the first set of flexible connectors 436 to unwind from shaft 434 and the other set of flexible connectors 440 to wind around shaft 438 to return the magnet 422 to the position shown in FIG. 11.

thereof; and means for moving the magnets 422 simul- The shafts 438 and 434 are housed respectively in the manifolds 426 and 428, and shaft 434 is connected with a variable speed DC motor. Shaft 438 is biased by springs 442 against rotation in a direction to permit the magnets 422 to move toward the right in FIG. 11.

Motor 432 can be connected with the shaft 434 through a gear reduction and automatic clutch device that provided for a dwell cycle of the magnet 422 at manifold 428, after which the shaft will be disengaged from motor 432 to permit the recoil springs 432 to return the magnets 422 to the starting position adjacent the manifold 426. The automatic clutch and gear reduction are illustrated schematically at 433 in FIG. 11.

As in the preceding embodiments, as the magnets 422 move from the starting position adjacent manifold 426 to the dwell position adjacent manifold 428, material carried with the magnets by the magnetic attraction thereof strikes the barrier 430 and is released from the field of the magnets 422 as the magnets 422 move past the barrier 430.

The magnets 422 in the embodiment of FIGS. 1 1 and 12 comprise a cylindrical body 444 with antifriction means carried by the body for supporting the body in the tube 420 in a substantially frictionless manner. The antifriction means is in the form of rollers 446 and 448 mounted on each end of the cylindrical body 444. The

inner surface of the tubular member 420 is of circular cross-section, and each of the rollers 446 and 448 has an outer, semi-spherical surface engaging the inner surface of the tubes 420, the semi-spherical surface of the rollers being substantially concentric with the inner surface of the tube 420. The rolling axis of roller 446 is angularly disposed about the longitudinal axis of the tube 420 from the rolling axis of roller 448.

FIGS. 13 and 14 illustrate the construction of a magnet 422' which is similar to the construction of the magnets 422 shown in FIGS. 11 and 12 except that the magnet 422'. is provided with seals for use in a fluid system such as shown in FIGS. 1 and 2. The magnet 422'. is received in a tube 420 and has a cylindrical body 444 with a roller 446 mounted at one'end and a roller 448 mounted at the other end. The roller 446 is mounted on a U-shaped bracket having a base portion 450 and a pair of leg portions 452. The roller 446 has a semi-spherical outer surface which is concentric with the tube 420, as shown particularly in FIG. 14. The roller- 446 rotates about a shaft 454 which extends through a bearing assembly 456 concentrically received in the roller 446. Roller 448 similarly is mounted on a U-shaped bracket having a base portion 460, leg portions 462, shaft 464 and bearing assembly 466. The construction of the roller 448 and its supporting structure is identical with that of roller 446 except that the shaft 464 is disposed at right angles to the shaft 454. Sealing members 472 are mounted in the circumferential grooves at opposite ends of the cylindrical body portion 444.

Thus, in each of the disclosed embodiments, a magnet is enclosed in and moves through a nonmagnetic tube, and the magnet can be sealed against outside contamination in each of the assemblies illustrated. The magnet can be caused to move through the nonmagnetic tube hydraulically, pneumatically, electrically or mechanically. The magnetic field from the magnet on the inside of the nonmagnetic tube collects and carries with it-ferrous metal or other magnetically attractive material, the magnetically attractive material being carried outside the nonmagnetic tube. As the magnet moves in a selected direction through the nonmagnetic tube, it carries the collected material with it to a barrier where movement of the collected material is interrupted and the magnet continues to move until the material is released from the magnetic field to fall into a collection bin or the like. The magnet can then be returned through the nonmagnetic tube to repeat its cycle. The magnetic element can be either a permanent magnet or an electromagnet.

In the embodiment of FIG. 11, for example, the connectors 436 may be in the form of insulated wire to carry current from a source of direct current to an electromagnet 422. Conductors may also be applied to the inner surface of the tubes 420 for sliding electrical engagement with electromagnetic elements movably mounted in the tubes. The magnetic element can be completely sealed from the surrounding environment permitting the apparatus to be inserted into liquids, powders, and preventing contamination from the ambient atmosphere.

While specific embodiments of the invention have been disclosed in the accompanying drawings and described in the foregoing specification, it should be understood that the invention is not limited to the exact construction shown. Alterations in the construction and arrangement of parts, all falling within the scope and spirit of the invention, will be apparent to those skilled in the art.

lclaim:

1. Apparatus for handling material by magnetic attraction comprising: an elongated tubular member of non-magnetic material; a magnet slidably received in said tubular member for movement along the length thereof between a starting position and a dwell position, said magnet being operable to attract articles of magnetically responsive material externally of said tubular member; means for selectively moving said magnet in said tubular member in opposite directions between said starting and dwell positions; a barrier engaging said tubular member between said starting and dwell positions for preventing articles and material attracted by said magnet from moving past the position of said barrier as the magnet moves to the dwell position; said magnet being in the form of a piston in generally fluid-tight relationship with the inner surface of said tubular member; and said means comprising a fluid system connected with said tubular member and selectively operable to cause fluid flow in opposite directions through said tubular member.

2. Apparatus as claimed in claim 1 wherein said fluid system includes a reservoir, a pump for delivering fluid from said reservoir, and a valve for controlling the direction of flow of fluid from said pump through said tubular member.

3. Apparatus for handling material by magnetic attraction comprising: a plurality of spaced, parallel tubes of nonmagnetic material; a magnet supported in each of said tubes for reciprocable movement along the length thereof; means for moving said magnets simultaneously in a selected direction through the respective tubes; and a transverse manifold at each end of said tubes securing said tubes together in spaced, parallel relationship, said magnets defining pistons in said tubes and said means comprising a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions in said tubes to cause corresponding movement of said magnets.

4. Apparatus as claimed in claim 3 including a barrier between said manifolds for stopping movement of articles or material attracted by said magnets as the magnets move between said manifolds.

5. Apparatus as claimed in claim 4 wherein said barrier comprises a sheet member having a plurality of apertures each closely receiving one of said tubes to thereby block passage of any material attracted by said magnets as said magnets pass said barrier.

6. Apparatus as claimed in claim 5 further including a collection chute of nonmagnetic material having its inlet end disposed adjacent said tubes and barrier to receive material released from the magnetic field of said magnets as the magnets move past said barrier.

7. Apparatus as claimed in claim 5 further including a roller of magnetic material mounted between each adjacent pair of tubes near said barrier for collecting material released from the magnetic field of the magnets in said tube as said magnets move past said barrier, and means for removing material from the surface of said rollers and conducting such material away from said tubes.

8. Apparatus as claimed in claim 7 wherein said last named means comprises a collection chute of nonmagnetic material having a plurality of slots each closely receiving one of said rollers to wipe material from the surface thereof.

9. Apparatus for separating magnetically attractive particles from nonmagnetic material comprising: a container for a mixture of magnetically attractive material and nonmagnetic material; a pair of spaced parallel manifolds of nonmagnetic material; a plurality of spaced, parallel tubes of nonmagnetic material extending between said manifolds, each end of each tube being in fluid communication with one of said manifolds; a magnetic piston in each of said tubes; a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions through said tubes to cause movement of said magnetic pistons in the same direction in said tubes; one of said manifolds being located in said container and the other of said manifolds being located outside said container; and a nonmagnetic barrier mounted on said tubes outside said container, said barrier being engageable by magnetically attractive material carried from said container by the magnetic attraction of said pistons as said pistons move from said one manifold toward said other manifold to release such material from the magnetic field of said pistons as the pistons move past said barriertoward said other manifold.

10. Apparatus as claimed in claim 9 further including a container for magnetically attractive material located to receive material falling from said barrier.

11. Apparatus as claimed in claim 9 further including a shaft mounted on said tubes and extending transversely with respect to said tubes; a plurality of rollers of magnetic material mounted on said shaft and spaced from each other such that each of said tubes is received,

between an adjacent pair of rollers, said shaft and rollet's being located outside said container on the side of said barrier opposite said other manifold to receive material falling from said barrier; and means for removing material from said rollers and conducting such material away from said rollers.

12. Apparatus as claimed inclaim 11 wherein said last named means comprises a chute having a slot for receiving each ofsaid rollers with the edges of the slots being disposed in close, wiping relationship with the respective rollers to wipe material from the surface thereof upon rotation of the roller. v

13. Apparatus for handling material by magnetic attraction comprising: an elongated tubular member of nonmagnetic material; a magnet slidably received in said tubular member for movement along the length thereof between a starting position and a dwell position, said magnetbeing operable to attract articles of magneticallyv responsive material externally of said tubular member; means for selectively moving said magnet in said tubular member in opposite. directions between said starting and dwell positions; abarrier engaging said tubular member between said starting and dwell positions for preventing articles and material attracted by said magnet frommoving past the position of said. barrier as the magnet moves to the dwell position; said magnet being in the form of a piston in generally fluid tight relationship with the inner surface of said tu-. bular member; said means comprising a fluid system connected with said tubular member and selectively operable to cause fluid flow in opposite directions through said tubular member; a powered roller of magnetic materialmounted on said tubular member on the oppositeside of said barrier member from said dwell position; and a collection tray of nonmagnetic material having a slot therein for receiving said roller andwiping magnetically attractive particles from 'the.surfacesof said roller.

14. Apparatus for handling material by magnetic attraction comprising: an elongated tubular, member of nonmagnetic material; a, magnet slidably received in said tubular memberfor movement alongthe length thereof between a starting position and a dwell position, said magnet being operable to attractarticles ofmagnetically responsivematerial externally of said tubular member; means for selectively moving said magnet in said tubular member in, opposite directions between said starting andrdwell positions; a barrier engaging said tubular member between said starting and dwell positions for preventing articles and material attracted by said magnet from moving past the position of said barrier as the magnet moves to the dwell position; said magnet being in the form of a piston in generally fluidtight relationship with the inner surface of said tubular member; said means comprising a fluid system connected with said tubular member and selectively operable to cause fluid flow in opposite directions through saidtubular member; and a magnetically attractive carrier supported externally on said tubular member for movement therealong in response to movement of said magnet.

15. Apparatus as claimed in claim 14 wherein said carrier comprises a sleeve member concentrically receiving said tubular member, and a plurality of balls supporting said sleeve on said tubular member.

16. Apparatus as claimed in claim 15 wherein said sleeve member and balls are of nonmagnetic material, and including magnetically attractive members mounted on each end of said sleeve member.

17. Apparatus as claimed in claim 14 wherein said carrier includes a bed portion supported for movement along said tubular member, and'a magnet carried by said bed portion for causing movement of said bed portion in response to movement of the magnet in said tubular member.

18. Apparatus as claimed in claim 17 wherein said bed portion is pivotal about an axis parallel to said tubular member.

19. Apparatus as claimed in claim 18 further including means for pivoting said bed portion to a dump position when the magnet in said tubular member has passed said barrier.

20. Apparatus for handling material by magnetic attraction comprising: a plurality of spaced, parallel tubes of nonmagnetic material; a magnet supported in each of said-tubes for reciprocable movement along the length thereof; means for moving said magnets simultaneously in a selected direction through the respective tubes; a'transverse manifold at each end of said tubes securing said tubes together in spaced, parallel relationship, said magnets defining pistons in said tubes and said means comprising a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions in said tubes to cause corresponding movement of said magnets; and a plurality of rollers each mounted between an adjacent pair of said tubes, said rollers being spaced from each other along the lengthof said tubes and each being rotatable about an axis transverse to said tubes with its periphery projecting beyond said tubes for engaging sheet material attracted by said magnets.

21. Apparatus as claimed in claim 20 wherein at least one of said rollers is of magnetic materialto inhibit transverse sliding of sheet material engaging said rollers.

22. Apparatus as claimed in claim 20 including a barrier member engageable by sheet material attracted to said tubes by said magnets to release such sheet material fromthe attraction of said magnets as said magnets pass said barrier during travel of said magnets through said tubes.

23. Apparatus for handling material by magnetic attraction comprising: a plurality of spaced, parallel tubes of nonmagnetic material; a magnet supported in each of said tubes for reciprocable movement along the length thereof; means for moving said magnets simultaneously in a selected direction through the respective tubes; a transverse manifold at each end of said tubes securing said tubes together in spaced, parallel relationship, said magnets defining pistons in said tubes and said means comprising a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions in said tubes to cause corresponding movement of said magnets; and magnetically attractive carrier means supported externally on said tubes for movement along the length thereof in response to movement of said magnets.

24. Apparatus as claimed in claim 23 wherein said carrier means comprises a carriage supported on said plurality of tubes for movement along the length thereof, and a plurality of magnetically attractive elements carried by said carriage to cause movement thereof in response to movement of said magnets within said tubes.

25. Apparatus as claimed in claim 24 wherein said magnetically attractive elements each comprises an external magnet projecting from said carriage between adjacent pairs of said tubes.

26. Apparatus as claimed in claim 25 including a retainer projecting from said carriage and receiving one of the outer tubes of said plurality of tubes to prevent displacement of said carriage from said one tube but permit said carriage to pivot about said one tube.

27. Apparatus as claimed in claim 26 including a plurality of spaced, parallel shafts mounted on said carriage and extending transversely of said tubes, and a plurality of rollers rotatably mounted on each of said shafts, each of said rollers engaging one of said tubes to movably support said carriage on said tubes.

28. Apparatus as claimed in claim 27 wherein the polarity of said external magnets is reversed with respect to the polarity of the magnets in said tubes.

29. Apparatus as claimed in claim 23 wherein said carrier means comprises a plurality of sleeve members, each of which is concentrically mounted on one of said tubes, and anti-friction means carried by each of said sleeve members supporting the sleeve member on the respective tubes.

30. Apparatus as claimed in claim 29 wherein said anti-friction means comprises a plurality of ball members carried by each sleeve member.

31. Apparatus as claimed in claim 30 including magnetically attractive material mounted on each end of said sleeve members. 

1. Apparatus for handling material by magnetic attraction comprising: an elongated tubular member of non-magnetic material; a magnet slidably received in said tubular member for movement along the length thereof between a starting position and a dwell position, said magnet being operable to attract articles of magnetically responsive material externally of said tubular member; means for selectively moving said magnet in said tubular member in opposite directions between said starting and dwell positions; a barrier engaging said tubular member between said starting and dwell positions for preventing articles and material attracted by said magnet from moving past the position of said barrier as the magnet moves to the dwell position; said magnet being in the form of a piston in generally fluid-tight relationship with the inner surface of said tubular member; and said means comprising a fluid system connected with said tubular member and selectively operable to cause fluid flow in opposite directions through said tubular member.
 2. Apparatus as claimed in claim 1 wherein said fluid system includes a reservoir, a pump for delivering fluid from said reservoir, and a valve for controlling the direction of flow of fluid from said pump through said tubular member.
 3. Apparatus for handling material by magnetic attraction comprising: a plurality of spaced, parallel tubes of nonmagnetic material; a magnet supported in each of said tubes for reciprocable movement along the length thereof; means for moving said magnets simultaneously in a selected direction through the respective tubes; and a transverse manifold at each end of said tubes securing said tubes together in spaced, parallel relationship, said magnets defining pistons in said tubes and said means comprising a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions in said tubes to cause corresponding movement of said magnets.
 4. Apparatus as claimed in claim 3 including a barrier between said manifolds for stopping movement of articles or material attracted by said magnets as the magnets move between said manifolds.
 5. Apparatus as claimed in claim 4 wherein said barrier comprises a sheet member having a plurality of apertures each closely receiving one of said tubes to thereby block passage of any material attracted by said magnets as said magnets pass said barrier.
 6. Apparatus as claimed in claim 5 further including a collection chute of nonmagnetic material having its inlet end disposed adjacent said tubes and barrier to receive material released from the magnetic field of said magnets as the magnets move past said barrier.
 7. Apparatus as claimed in claim 5 further including a roller of magnetic material mounted between each adjacent pair of tubes near said barrier for collecting material released from the magnetic field of the magnets in said tube as said magnets move past said barrier, and means for removing material from the surface of said rollers and conducting such material away from said tubes.
 8. Apparatus as claimed in claim 7 wherein said last named means comprises a collection chute of nonmagnetic material having a plurality of slots each closely receiving one of said rollers to wipe material from the surface thereof.
 9. Apparatus for separating magnetically attractive particles from nonmagnetic material comprising: a container for a mixture of magnetically attractive material and nonmagnetic material; a pair of spaced parallel manifolds of nonmagnetic material; a plurality of spaced, parallel tubes of nonmagnetic material extending between said manifolds, each end of each tube being in fluid communication with one of said manifolds; a magnetic piston in each of said tubes; a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions through said tubes to cause movement of said magnetic pistons in the same direction in said tubes; one of said manifolds being located in said container and the other of said manifolds being located outside said container; and a nonmagnetic barrier mounted on said tubes outside said container, said barrier being engageable by magnetically attractive material carried from said container by the magnetic attraction of said pistons as said pistons move from said one manifold toward said other manifold to release such material from the magnetic field of said pistons as the pistons move past said barrier toward said other manifold.
 10. Apparatus as claimed in claim 9 further including a container for magnetically attractive material located to receive material falling from said barrier.
 11. Apparatus as claimed in claim 9 further including a shaft mounted on said tubes and extending transversely with respect to said tubes; a plurality of rollers of magnetic material mounted on said shaft and spaced from each other such that each of said tubes is received between an adjacent pair of rollers, said shaft and rollers being located outside said container on the side of said barrier opposite said other manifold to receive material falling from said barrier; and means for removing material from said rollers and conducting such material away from said rollers.
 12. Apparatus as claimed in claim 11 wherein said last named means comprises a chute having a slot for receiving each of said rollers with the edges of the slots being disposed in close, wiping relationship with the respective rollers to wipe material from the surface thereof upon rotation of the roller.
 13. Apparatus for handling material by magnetic attraction comprising: an elongated tubular member of nonmagnetic material; a magnet slidably received in said tubular member for movement along the length thereof between a starting position and a dwell position, said magnet being operable to attract articles of magnetically responsive material externally of said tubular member; means for selectively moving said magnet in said tubular member in opposite directions between said starting and dwell positions; a barrier engaging said tubular member between said starting and dwell positions for preventing articles and material attracted by said magnet from moving past the position of said barrier as the magnet moves to the dwell position; said magnet being in the form of a piston in generally fluid tight relationship with the inner surface of said tubular member; said means comprising a fluid system connected with said tubular member and selectively operable to cause fluid flow in opposite directions through said tubular member; a powered roller of magnetic material mounted on said tubular member on the opposite side of said barrier member from said dwell position; and a collection tray of nonmagnetic material having a slot therein for receiving saiD roller and wiping magnetically attractive particles from the surfaces of said roller.
 14. Apparatus for handling material by magnetic attraction comprising: an elongated tubular member of nonmagnetic material; a magnet slidably received in said tubular member for movement along the length thereof between a starting position and a dwell position, said magnet being operable to attract articles of magnetically responsive material externally of said tubular member; means for selectively moving said magnet in said tubular member in opposite directions between said starting and dwell positions; a barrier engaging said tubular member between said starting and dwell positions for preventing articles and material attracted by said magnet from moving past the position of said barrier as the magnet moves to the dwell position; said magnet being in the form of a piston in generally fluid tight relationship with the inner surface of said tubular member; said means comprising a fluid system connected with said tubular member and selectively operable to cause fluid flow in opposite directions through said tubular member; and a magnetically attractive carrier supported externally on said tubular member for movement therealong in response to movement of said magnet.
 15. Apparatus as claimed in claim 14 wherein said carrier comprises a sleeve member concentrically receiving said tubular member, and a plurality of balls supporting said sleeve on said tubular member.
 16. Apparatus as claimed in claim 15 wherein said sleeve member and balls are of nonmagnetic material, and including magnetically attractive members mounted on each end of said sleeve member.
 17. Apparatus as claimed in claim 14 wherein said carrier includes a bed portion supported for movement along said tubular member, and a magnet carried by said bed portion for causing movement of said bed portion in response to movement of the magnet in said tubular member.
 18. Apparatus as claimed in claim 17 wherein said bed portion is pivotal about an axis parallel to said tubular member.
 19. Apparatus as claimed in claim 18 further including means for pivoting said bed portion to a dump position when the magnet in said tubular member has passed said barrier.
 20. Apparatus for handling material by magnetic attraction comprising: a plurality of spaced, parallel tubes of nonmagnetic material; a magnet supported in each of said tubes for reciprocable movement along the length thereof; means for moving said magnets simultaneously in a selected direction through the respective tubes; a transverse manifold at each end of said tubes securing said tubes together in spaced, parallel relationship, said magnets defining pistons in said tubes and said means comprising a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions in said tubes to cause corresponding movement of said magnets; and a plurality of rollers each mounted between an adjacent pair of said tubes, said rollers being spaced from each other along the length of said tubes and each being rotatable about an axis transverse to said tubes with its periphery projecting beyond said tubes for engaging sheet material attracted by said magnets.
 21. Apparatus as claimed in claim 20 wherein at least one of said rollers is of magnetic material to inhibit transverse sliding of sheet material engaging said rollers.
 22. Apparatus as claimed in claim 20 including a barrier member engageable by sheet material attracted to said tubes by said magnets to release such sheet material from the attraction of said magnets as said magnets pass said barrier during travel of said magnets through said tubes.
 23. Apparatus for handling material by magnetic attraction comprising: a plurality of spaced, parallel tubes of nonmagnetic material; a magnet supported in each of said tubes for reciprocable movement along the length thereof; means for moving said magnets simultaneously in a selected direction through the respective tubes; a transvErse manifold at each end of said tubes securing said tubes together in spaced, parallel relationship, said magnets defining pistons in said tubes and said means comprising a fluid flow system connected with said manifolds selectively operable to cause fluid flow in opposite directions in said tubes to cause corresponding movement of said magnets; and magnetically attractive carrier means supported externally on said tubes for movement along the length thereof in response to movement of said magnets.
 24. Apparatus as claimed in claim 23 wherein said carrier means comprises a carriage supported on said plurality of tubes for movement along the length thereof, and a plurality of magnetically attractive elements carried by said carriage to cause movement thereof in response to movement of said magnets within said tubes.
 25. Apparatus as claimed in claim 24 wherein said magnetically attractive elements each comprises an external magnet projecting from said carriage between adjacent pairs of said tubes.
 26. Apparatus as claimed in claim 25 including a retainer projecting from said carriage and receiving one of the outer tubes of said plurality of tubes to prevent displacement of said carriage from said one tube but permit said carriage to pivot about said one tube.
 27. Apparatus as claimed in claim 26 including a plurality of spaced, parallel shafts mounted on said carriage and extending transversely of said tubes, and a plurality of rollers rotatably mounted on each of said shafts, each of said rollers engaging one of said tubes to movably support said carriage on said tubes.
 28. Apparatus as claimed in claim 27 wherein the polarity of said external magnets is reversed with respect to the polarity of the magnets in said tubes.
 29. Apparatus as claimed in claim 23 wherein said carrier means comprises a plurality of sleeve members, each of which is concentrically mounted on one of said tubes, and anti-friction means carried by each of said sleeve members supporting the sleeve member on the respective tubes.
 30. Apparatus as claimed in claim 29 wherein said anti-friction means comprises a plurality of ball members carried by each sleeve member.
 31. Apparatus as claimed in claim 30 including magnetically attractive material mounted on each end of said sleeve members. 